1. Field of the Invention
The present invention relates to a method for forming a mask pattern in a semiconductor manufacturing process, and more particularly, to the improvement of a method for correcting the mask pattern.
2. Description of the Related Art
Recently, as semiconductor devices have been very fine-structure a, the errors of a photoresist pattern caused by the optical proximity effect of a light exposure system and the developing process cannot be ignored.
In a first prior art mask pattern forming method (see JP-A-4-179952), a light intensity on a photoresist layer with respect to a position is calculated. Then, a correction amount of the position is calculated by determining whether or not the light intensity reaches a definite value. Then, the dimension of the pattern of the pattern mask is corrected in accordance with the correction amount. This will be explained later in detail.
Thus, in the first prior art mask pattern forming method, an error of a photoresist pattern due to the optical proximity effect can be corrected. However, since no consideration is given to a developing process of the photoresist layer, a change of a photoresist pattern due to the change of a light intensity distribution by the developing process of the photoresist layer cannot be corrected.
In a second prior art mask pattern forming method (see JP-A-6-45424), a relationship between a dissolving speed and an exposure with respect to a depth position of a photoresist layer are experimentally obtained in advance. First, light intensity for points of the photoresist layer is calculated to obtain an exposure distribution. Then, a dissolving speed of each point within the photoresist layer is calculated by using this relationship, and thus, a dissolving speed distribution within the photoresist layer is obtained. Then, a developing time (dissolving time) of each point within the photoresist layer is calculated by using the dissolving speed distribution, and thus, a developing time distribution within the photoresist layer is obtained. Then, a photoresist pattern is calculated by setting a time contour having the same time as the developing time distribution. Then, the dimension of the pattern of the pattern mask is corrected in accordance with the calculated photoresist pattern. This will be explained later in detail.
Thus, in the second prior art mask pattern forming method, a change of a photoresist pattern due to the change of a light intensity distribution by the developing process of the photoresist layer can be corrected. However, since a dissolving speed and a developing time are calculated for each point of the photoresist layer, a large amount of calculating time is required.